W. E. Splinter in U.S. Pat. No. 3,093,949 discloses a tobacco leaf defoliator assembly that is commonly referred to today as a knife head type defoliator. Structurally the Splinter Knife Head Defoliator comprises a pair of inclined and laterally spaced defoliator units that in operation are generally disposed on opposite sides of a tobacco row, and are designed to allow the individual stalks of the row to pass therethrough as the defoliator assembly is moved along the tobacco row by a tobacco harvester.
From a study of the Splinter disclosure, it will be seen that as the defoliator assembly moves along the tobacco row certain sets of knife blades move inwardly from opposite sides of the row to project through the plane of the tobacco row adjacent and between the respective stalks passing through the defoliator assembly. After the knife blades have moved to a position where they project adjacent and between successive stalks, the defoliator assembly then drives these blades upwardly and rearwardly relative to the harvester. As the blades move upwardly adjacent respective stalks, they engage certain tobacco leaves extending from the stalks and defoliate them therefrom, while the rearward component enables the blade to move rearwardly as the harvester moves forwardly. Because certain sets of knife blades at least partially surround the stalk while the defoliator assembly is moving along the row, the horizontal speed which may be referred to as the horizontal speed component of the knives projecting into the plane of the stalk row during defoliation, should generally be equal and opposite the forward ground speed of the harvester. It is appreciated that if the horizontal speed or movement of the knives is significantly faster or slower than the ground speed of the harvester that the knives will engage, bend and even cut through the stalks, thereby seriously damaging the tobacco crop.
In driving the Splinter type knife defoliator some form of a speed relationship should exist between the speed of the defoliator assembly and the ground speed of the tobacco harvester carrying the defoliator assembly. But how to establish a definite and continuous speed relationship between the defoliator assembly and the harvester ground speed has been the principal problem confronted by the Splinter type knife defoliator, and the lack of such a speed control system has been responsible, in part at least, for the failure of the Splinter defoliator to gain complete farmer acceptance.
The Splinter Knife Defoliator has been used in the past as a defoliator head for automatic tobacco harvesters. Such harvesters have utilized a hydraulic drive for driving the Splinter Defoliator, and for varying the speeds thereof there has been provided a purely manual control disposed adjacent the operator's station. As the harvester moves through the field, the operator has the responsibility of judging the harvester ground speed and manually adjusting the speed of the defoliator to where the rearward horizontal speed of the knives is thought to be approximately equal to the harvester ground speed. Alternatively in such cases, the operator in some instances may set the defoliator speed at a constant speed and attempt to adjust the ground speed of the harvester to a speed that will approximately equal the horizontal speed component of the knives.
Needless to say, such methods of controlling the defoliator speed are quite imprecise, and often impractical and essentially unworkable except with the most skilled operators. During the harvesting operation, the operator must give his attention to steering the harvester through the field, and observing the defoliator and leaf conveying processes that are taking place. There is not sufficient time under ordinary conditions to give proper attention to these tasks, and other routine operator responsibilities and also to continuously judge the ground speed of the harvester and attempt to adjust the speed of the defoliator to synchronize the knives with the passing stalks. This is even more difficult because in the tobacco harvesting operation there are numerous occasions where the speed of the harvester changes and often these changes are very sudden and abrupt changes. For example, at the beginning and end of each row, the speed of the harvester is sometimes slower than the average speed in the open field since the operator must negotiate turning at the end of each row. Also, it becomes necessary to slow down the harvester in the open field due to gullies or other type of irregularities in field terrain. In such situations to avoid the cutting of the stalks, it is necessary for the operator to foresee these changes in ground speed and to timely make the proper manual speed adjustments for the defoliator at the same time the harvester is either speeding up or slowing down in order to avoid substantial damage to the tobacco crop. Even in cases where the operator is skilled and has extensive field experience with such a manual control, it is not possible for the operator to continuously and precisely manually control the speed of the defoliator assembly relative to harvester ground speed, and thus there will always be some crop damage. Skilled and experienced operators are not plentiful or readily available and therefore the operators of such tobacco harvesters are usually unskilled and inexperienced. In these situations, one can expect substantial crop damage where the unskilled and inexperienced operator has to manually control the speed of the defoliator assembly based solely on a judgment of harvester ground speed.